Considerable research and development has been previously conducted in the fields of tissue characterization, medical imaging and computerized surgical planning and/or guidance. The following listing of reference is presented as being generally indicative of the types of technology known to those of ordinary skill in the art. The list does not purport to be exhaustive.
Variations in electrical impedance of the human tissue are described in the patent literature to provide indications of tumors, lesions and other abnormalities. For example, U.S. Pat. Nos. 4,291,708; 4,458,694; 4,537,203; 4,617,939 and 4,539,640 exemplify systems for tissue characterization by using multi-element probes which are pressed against the skin of the patient and measure impedance of the tissue to generate a two-dimensional impedance map.
Other techniques of this type are described in WO 01/43630 and in U.S. Pat. Nos. 4,291,708 and 5,143,079.
U.S. Pat. Nos. 5,807,257; 5,704,355 and 6,061,589 describe use of millimeter and microwave devices to measure bioimpedance and to detect abnormal tissue. These methods direct a free propagating radiation, or a guided radiation via waveguide, onto the organ. The radiation is focused on a relatively small volume inside the organ, and the reflected radiation is then measured.
U.S. Pat. No. 6,109,270 describes a measurement concept with a multi-modality instrument for tissue identification in real-time neuro-surgical applications.
U.S. Pat. Nos. 6,813,515; 7,082,325 and 7,184,824 U.S. Patent Applications published as 20070255169; 20070179397; 20070032747; 20070032739; 20060264738; 20060253107; 20050021019; 20030187366 and 20030138378 describe tools systems and methods useful in assessing tissue type and/or identifying tumor margins.
U.S. Pat. No. 5,615,132 describes a method and apparatus for determining position and orientation of a moveable object using accelerometers.
U.S. Pat. No. 6,833,814 describes an intrabody navigation system for medical applications in which three planar antennas that at least partly overlap are used to transmit electromagnetic radiation simultaneously.
Ascension Technology Corp. (Burlington Vt., USA) markets a guide for localizing medical instruments with 3D magnetic tracking as “3D Guidance™ Medsafe”.